Hard-line conservatives are rising out of the ashes of a weekslong government shutdown, emboldened by the possibility of adding to their ranks in the Senate next year — whether by picking up Democrat-held seats or taking out Republican incumbents.

Just two Republican senators have lost in primaries in the last two election cycles, but that's not stopping a growing number of intraparty challengers this cycle. Conservative third-party groups and candidates hope to give more backup to folks like Sens. Ted Cruz of Texas and Mike Lee of Utah, who led an effort to defund the health care law.

The GOP brand overall may have taken a significant hit this month and caused at least some concern within the party about obtaining or keeping the majority in either chamber in the next couple of election cycles. But the shutdown only fueled challenges to sitting Republicans.

It's still too early to know exactly how competitive many of the challengers can be. At this point, there is a big difference in the competitiveness of the races from the top three to bottom three on this list. And as the most recent fundraising reports to the Federal Election Commission illustrated, nearly all of the incumbents’ opponents are starting out in deep financial holes.

Still, with outside groups such as the Club for Growth and the Senate Conservatives Fund beginning to engage, a challenger’s money isn’t the only threat — and any of these races could theoretically take off.

Here are the seven Republican senators most vulnerable to a primary challenge, in order:

1. Michael B. Enzi, Wyoming

2. Mitch McConnell, Kentucky

This primary race won’t just decide the fate of the minority leader, it also plays a determining factor in the future of the GOP. McConnell’s decision to strike a deal with Senate Majority Leader Harry Reid, D-Nev., to reopen the federal government and avoid default invited immediate disparagement from his primary opponent and conservative groups. But Louisville businessman Matt Bevin, whom the Senate Conservatives Fund endorsed last week, starts out

. McConnell’s decision to strike a deal with Senate Majority Leader Harry Reid, D-Nev., to reopen the federal government and avoid default invited immediate disparagement from his primary opponent and conservative groups. But Louisville businessman Matt Bevin, whom the Senate Conservatives Fund endorsed last week, starts out far behind after one fundraising quarter. Bevin loaned his campaign $600,000 to help get it off the ground. One thing to watch is how much of his nearly $10 million in the bank McConnell will have to expend staving off Bevin in the primary. Should he prevail, McConnell will face Democrat Alison Lundergan Grimes in the general.

far behind after one fundraising quarter. Bevin loaned his campaign $600,000 to help get it off the ground. One thing to watch is how much of his nearly $10 million in the bank McConnell will have to expend staving off Bevin in the primary. Should he prevail, McConnell will face Democrat Alison Lundergan Grimes in the general.

3. Thad Cochran, Mississippi

This name could leap off the list by the end of this year, as Cochran hasn’t even announced whether he’ll seek re-election. His third-quarter report offered no evidence that he intends to run again, as he raised just $53,000. But the veteran appropriator would likely have no trouble turning on the fundraising engine. Still, outside groups last week quickly endorsed the candidacy of his primary opponent, state Sen. Chris McDaniel. And the Club for Growth

whether he’ll seek re-election. His third-quarter report offered no evidence that he intends to run again, as he raised just $53,000. But the veteran appropriator would likely have no trouble turning on the fundraising engine. Still, outside groups last week quickly endorsed the candidacy of his primary opponent, state Sen. Chris McDaniel. And the Club for Growth is already on TV introducing McDaniel to the state.

4. Lindsey Graham, South Carolina

Graham’s top primary challengers have so far raised a fraction of what the second-term senator has been able to bring in this year. But conservative state Sen. Lee Bright and Nancy Mace, the first female graduate of the Citadel, nonetheless see an opportunity against the senator with a record of bipartisan deal-making. The goal for each is to face Graham one-on-one in the runoff, when anything could happen.

5. Pat Roberts, Kansas

6. Lamar Alexander, Tennessee

7. John Cornyn, Texas

Cornyn barely makes this list and will likely be expunged by December. After Cruz’s surprising primary victory last year, Cornyn, now the Senate minority whip, appeared to be among the most vulnerable to an intraparty challenge. But Cornyn is two months from the candidate filing deadline and has so far avoided gaining a significant opponent. Cornyn, who wields a similar voting record to Cruz this year, voted against the deal last week that reopened the government.

But Cornyn is two months from the candidate filing deadline and has so far avoided gaining a significant opponent. Cornyn, who wields a similar voting record to Cruz this year, voted against the deal last week that reopened the government.